Atresia ani (AA) is a rare congenital anomaly that occurs in kittens and puppies (2,3,5,6). Only a few patients with AA and rectovaginal or rectovestibular fistula between the distal urogenital tract and the rectum have been reported. Congenital anomalies of the anus and rectum associated with urogenital malformations originate from anomalous embryonic development of the cloacal region (7,9,11). Initially, the gastrointestinal, urinary, and reproductive tracts communicate, forming the cloaca. As the embryo develops, the urorectal fold grows caudally and separates the urogenital and rectal tracts. Finally, the anal membrane thins and ruptures, creating an anus. Failure of the anal membrane to perforate after anal formation or failure of the urorectal fold to separate the primitive cloaca causes AA.

Four types of AA have been reported. Congenital anal stenosis was classified as type 1. Patients with type 2 AA have a membrane over the anal opening, which is also known as imperforate anus. Type 3 is similar to type 2, but has more cranial termination of the rectum as a blind pouch. Animals with type 4 AA may have normal development of the anus and terminal rectum with discontinuity of the proximal rectum (1). Types 3 and 4 are also classified as segmental rectal aplasia or rectal atresia (8). A rectovaginal fistula is most often observed in type 2 AA (3). The external anal sphincter and anal sac normally develop in type 2 anomalies. Unlike type 2, type 3 anomalies have abnormal external anal sphincter, anal sac, or tail (4). These anomalies have been reported in veterinary textbooks, but only a small number of cases (2,4,19). The clinical signs of AA start within a few weeks after birth. Signs, such as the passage of feces through the vulva, irritation of the vulva, tenesmus, cystitis, and megacolon, are commonly found (16,21). Depending on the poor general condition, age, and size of the patients, anesthesia and surgery can become challenging (12). Patients with type 1 AA, treated with a liquid diet, will not be clinically evident (22). However, most patients with AA show obvious clinical signs. Radiographic examination with vaginogram, infusing contrast medium through the vagina or fistula, may be helpful for a detailed diagnosis.

Only a few reports of AA in cats have been reported in the literature (8,14,20), since the incidence is low and affected cats are euthanized at an early age based on the perception that surgical correction is unrewarding. As reported in a review in the Veterinary Medical Database, AA accounts for 0.007% of cases in dogs, in which females are more likely to be affected than males (19). In cats, females are also more commonly affected than males (4). More information is needed to make recommendations to veterinarians, plan surgery, and predict prognosis.

Syringe ports are introduced as a safe alternative to costly disposable circular retractors or dilators in human neurosurgery (16,17). A simple method using a cylindrical channel retractor custom made of a plastic syringe helps to retract. In this case, a 1-cc syringe port was used to retract the anal canal and avoid stenosis.

The purpose of this study was to introduce a surgical technique using a 1 cc syringe port in a kitten with type 3 AA and rectovaginal fistula to minimize complications.

A 2-month-old, 740 g intact female domestic shorthair was admitted for evaluation of vaginal discharge. The owner observed that the kitten was dripping feces and urine together from the vagina. On physical examination, the kitten defecated liquid feces from the vulva and anus were imperforate. The perineal reflex was evaluated by gently touching the perineal area using forceps. No perineal reflex was observed. During abdominal palpation, a distended colon can be palpated. Anal dimples were observed where the anus was normally located (Fig. 1).

Figure 1. An anal dimple. A 2-month-old female domestic shorthair with type 3 atresia ani. The arrow points to an anal dimple.

Vaginogram was performed using a tomcat urinary catheter and 5 mL of iodine contrast medium (Iohexol 65%; Omnipaque 300, GE Healthcare SA, France). Lateral and ventrodorsal projections in the kitten showed contrast medium passing into the colon from the vagina through a small fistula (Fig. 2). The X-ray revealed a megacolon due to abnormal distention of the descending colon. The thickest part of the megacolon was 2.7 cm in lateral view. Computed tomography (CT) angiography was performed for a more detailed diagnosis (Fig. 3). Following CT and physical examination, the patient was diagnosed with type 3 AA with rectovaginal fistula.

Figure 2. Vaginogram in the lateral projection of the abdomen. Contrast medium filling the colon from the vagina. The megacolon is identified.

Figure 3. Computed tomography (CT) angiography is performed for a more detailed diagnosis. The patient is diagnosed with type 3 atresia ani with a rectovaginal fistula. Imperforate anus with the rectum terminating in a blind pouch (yellow arrow) approximately 1.26 cm below the perineal skin was observed in the CT findings.

The kitten was premedicated with atropine, 0.04 mg/kg, SC (Atropine^®, Jeil Pharmaceutical Co., Daegu, Korea); medetomidine, 0.02 mg/kg, SC (Domitor^®; Pfizer, NY, USA); acepromazine, 0.05 mg/kg, SC (Sedaject^®; Samu Median, Seoul, Korea); and propofol, l5 mg/kg, IV (Provive 1%^®, Baxter, Vasana, India). Anesthesia was maintained using a mixture of 2.0-3.0% isoflurane (Terrell^TM, Piramal Critical Care, USA) and oxygen. The position was in sternal recumbency. The tail was fixed with a tape on the back and the pelvis was elevated for better visualization. The surgical area was clipped and prepared for surgery. Cephazolin (23 mg/kg, IV; Cephazolin^®, Hankook Korus Pharm Co., Seoul, Korea) was administered before surgery. The cat was prepared aseptically and placed in ventral recumbency. The anus was elevated and rigid fixation of the body was possible using a vacuum bean bag. A tomcat urinary catheter was inserted into the vulva to find a rectovaginal fistula. However, the fistula was too small and could not be identified. Therefore, a simple anoplasty was performed on the imperforated anus. The incision was made in the imperforated rectal portion using a #11 scalpel blade. The rectal pouch was identified through an incision. The pouch was resected and sutured to the skin at the level of the external anal sphincter. Seven 4-0 nylon simple interrupted sutures were used to reconstruct the anal canal and anus. Feces in the distal colon were flushed out using a feeding tube instead of a colotomy (Fig. 4). The anal opening was reconstructed without tension, and a 1-cc syringe port (finger flange and plunger) was used to minimize complications related to tension, which can cause wound dehiscence and stenosis (Fig. 5).

Figure 4. A feeding tube is used to empty the distal colon. Feces in the distal colon is flushed out using a feeding tube.

Figure 5. A 1-cc syringe port is used in anoplasty surgery. (A) The anal opening is reconstructed without tension and the 1-cc syringe port was used to minimize complications related to stenosis. (B) The 1-cc syringe port before suturing in the surgical area.

A lateral view of the abdominal X-ray was performed to check the emptied distal colon. Postoperatively, meloxicam (2.2 mg/kg, PO; Metacam^®, Boehringer Ingelheim, Mexico), cefadroxil (25 mg/kg, PO; Cefaxil^®; Koruspharm, Jecheon, Korea), famotidine (0.5 mg/kg, PO; Famotidine^®; NELSON, Korea), and lactulose (0.5 mL, PO; Duphalac, JW Pharmaceutical, Seoul, Korea) were administered twice a day. Since the surgical area was difficult to keep clean due to the feces and syringe port, the syringe tip was removed from the surgical area after 5 days. Furthermore, to keep the surgical area clean, a lavage was performed twice a day with 0.9% normal saline using an 18-gauge needle.

The patient was unable to defecate normally during the immediate postoperative period. Dyschezia was observed during the first 3 days. Lactulose was administered orally for 5 days to resolve dyschezia. The syringe port was removed 5 days after surgery. After removal of the tip of the syringe, no wound dehiscence, anal stenosis, or other complications were observed, except fecal incontinence. After 3 weeks, an abdominal radiography was performed to check the distal colon (Fig. 6). The patient had constipation, but the diameter of the colon lumen was reduced than in the immediate preoperative period. Conservative treatment was first attempted. Lactulose (0.5 mL) and a low-residue diet were administered. At 3-month of telephone follow-up after surgery, the cat was reported to have no other clinical signs.

Figure 6. An abdominal radiograph was performed to check the distal colon 3 weeks postoperatively.

All four types of AA cause secondary complications if surgical treatment is not performed at the appropriate time. The most frequently detected secondary complications include megacolon, ascending urinary tract infection, and chronic renal damage (3). It is important to make a delicate classification that leads to appropriate surgical planning. Surgical planning, preoperative treatment, and postoperative treatment are also critical in these patients and can result in a better prognosis.

To perform anoplasty in type 3 AA, it is necessary to use the portion of the rectum located cranial to the imperforated anus. Simple anoplasty is an option for reconstruction (13). Recently, some studies postulated that such extensive dissection has been responsible for complications of type 3 AA and rectovaginal fistula in cats. The best option is to use a fistula to reconstruct the anal canal (8,14). However, it is believed that separation of the vagina and rectum and precise identification of the external anal sphincter are difficult through this small incision. Sometimes, surgery on fistulas cannot be performed due to the poor condition of the fistula or the small size of the fistula (8). Therefore, veterinarians need more information to reduce the incidence of complications related to pull tension and stenosis of the rectum.

A 1-cc syringe flange port was used to retract the anal canal after surgery. In human neurosurgery, customized syringe ports are used as a cost-effective and safe alternative to costly disposable brain port systems (15,16). Syringe ports have been used as safe retractors in the human brain with great outcomes. This indicates that the use of custom-made syringe ports in fragile tissues is possible without causing major complications. Anoplasty with excessive tissue damage can create scar tissue in the surgical area and reduce the size of the anal canal. Furthermore, the rectal position far cranial to the imperforated anus makes surgery difficult and creates tension in the surgical area (10,18). Retraction of the surgical area provided by the customized syringe port can prevent complications related to stenosis without critical damage. The syringe port in this case report was kept for only 5 days because the feces were clogged between the surgical area and the syringe port. To keep the surgical area clean, a frequent lavage procedure, using 0.9% normal saline, is indicated. After surgery, abdominal radiography should be performed to check for an empty distal colon for a better prognosis (4).

Long-term follow-up is needed for more patients with AA (23). More studies are needed to determine the optimal surgical planning for puppies and kittens with AA. More experience with this surgery is necessary to improve the prognosis of this surgical treatment.

In this case report, a kitten with type 3 AA with rectovaginal fistula was successfully repaired by anoplasty with a 1-cc syringe port and flushing of feces using a feeding tube. This case report demonstrates a technique to reduce complication rates in rectovaginal fistula surgery in a kitten.

The authors have no conflicting interests.